Many textile machines utilize a disk type of yarn tension device wherein the yarn runs between a pair of metal disks with one disk being resiliently urged against the yarn and toward the other disk by a compression spring. The amount of compressive force applied by the spring can be adjusted to vary the tension placed on the running yarn. This disk type of tension device has been in use for many years and operates satisfactorily in some applications but has a tendency to collect lint from the running yarn and the accumulated lint causes variations in tension of the yarn.
It is also generally known to position plate members on opposite sides of a running yarn to apply tension to the yarn passing therebetween. For example, this general type of tensioning device is illustrated in U.S. Pat. No. 1,564,995 wherein a yarn is tensioned by passing the same between a pair of corrugated plate members and one of the plate members is provided with a plurality of openings in each of the valleys of the corrugations so that the amount of tension placed on the yarn is varied by feeding the yarn upwardly through various ones of the opennings in the corrugations. U.S. Pat. No. 2,339,854 discloses a tension device which includes a corrugated back plate and a spring steel front plate with the yarn passing therebetween to apply tension thereto. The tension device of U.S. Pat. No. 2,451,889 includes a pair of wedge shaped plates supported in a guide so that the yarn may be passed between the plates at various positions and to thereby vary the length of travel of the yarn between the wedge shaped plates and to thereby change the tension applied thereto. In U.S. Pat. No. 2,643,831 the yarn passes between a pair of thin flexible plate members which may be bowed to various adjusted positions to vary the tension of the yarn passing therebetween.
A cable brake device is disclosed in U.S. Pat. No. 3,057,438 which includes a pair of opposed frictional rubber brake plates for engaging opposite sides of the cable and one of the brake plates is supported for inward and outward adjusted resilient engagement with the cable passing therebetween to vary the tension placed thereon. In the tension device of U.S. Pat. No. 3,144,997 the yarn runs over a glass plate and a plurality of friction pads are resiliently urged against the yarn to vary the pressure or resistance to movement of the yarn along the glass plate. U.S. Pat. No. 3,340,903 discloses a tensioning device which includes a wear resistant hard plate member over which the yarn passes and a flexible steel plate overlying the hard plate and being moved into resilient engagement with the yarn passing therebetween. The tension device of U.S. Pat. No. 3,633,711 includes a relatively thin steel strip overlying a foam backing and over which the yarn passes. A plurality of brake fingers is resiliently urged against the opposite side of the yarn and press the same into engagement with the steel sheet to apply tension to the yarn passing therebetween. U.S. Pat. No. 4,313,578 discloses one embodiment of a tension control device utilizing a pair of plate members having their adjacent inner faces positioned on opposite sides of the running yarn. One plate member is urged against the yarn and toward the other plate member by means of electromagnetic attraction to thereby apply tension to the yarn passing between the plate members.
The yarn tension devices of these prior patents also have generally the same problem associated with the well known disk type tension devices in that they tend to collect fiber particles and lint between the plate members and the accumulated lint can cause the tension applied to the yarn to be considerably varied. Also, many of the devices of these prior patents are difficult to clean and remove the lint therefrom. Further, it is difficult to thread the yarn through these prior art devices and to then properly regulate the tension being placed on the running yarn.